Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Patent
1992-08-17
1995-02-28
Asher, Kimberly L.
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
12820522, 12820127, 12820222, 367 6, 367 21, 367 77, 340297, 340298, A62B 700, A62B 900, B63C 1102, G08B 300
Patent
active
053927710
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a monitoring device for portable breathing apparatuses. Portable breathing apparatuses of this kind are used for example by divers, by fire fighters when fighting fires or generally whenever air is charged with noxious substances which make unaided breathing impossible. Portable breathing apparatuses usually consist of one or two metal bottles which are carried for example on the back of the user and in which a highly compressed oxygen gas mixture at a pressure of for example 350 bar is contained. This oxygen gas mixture is designated below, for the sake of simplification, as breathing air or simply as air. The breathing air is removed from the bottles via a shut-off valve and breathed in by the user by means of a so-called demand valve.
The problem in using breathing apparatuses of this kind is initially described by reference to the example of scuba diving:
In professional scuba diving today depths of over one hundred meters are reached and, even when diving as a hobby, experienced divers go down to considerable depths.
As the depth of water increases, the hydrostatic pressure acting on the diver becomes greater, which leads to the body tissues absorbing a relatively high amount of inert gases, that is to say in particular nitrogen. During resurfacing and the associated pressure reduction this process is reversed. If the pressure reduction occurs more quickly than the gas, which is being released, can be carried off and breathed out, decompression sickness occurs which in less severe cases leads to temporarily-health but in more severe cases can lead to permanent damage to health and even to death. In order to prevent a rapid release of the inert gases, when returning to the surface after a relatively long time spent at a relatively great depth divers must therefore remain at specific depths for relatively long resurfacing interludes which are referred to as so-called decompression stops. The duration of the necessary decompression stops is difficult to calculate since the human body has a multiplicity of different types of tissue which differ both with respect to the saturation and desaturation behavior as a function of the diving depth and duration of diving and also with respect to the medical hazard. Therefore, divers usually use diving tables in which the decompression times are given as a function of the diving depth reached and the duration of diving or they use diving computers in which the saturation and desaturation behavior of a selected number of types of tissue are mathematically simulated and the decompression times thus calculated are displayed to the driver via corresponding display devices.
A summary of the problems of decompression is given, for example, by the publication by A.A. Buhlmann: Decompression--Decompression Sickness, Berlin, Heidelberg, New York, Tokyo 1984, ISBN 3-540-13308-9, specifically in particular pages 1-62 for the medical aspect and pages 63-67 for the decompression calculation. Pages 68-82 contain decompression tables for divers.
Therefore, before the diver undertakes such a dive he must ensure that the air supply he carries is adequate for the planned bottom time and for the ascent time.
However, determining the required air supply is faced with considerable difficulties: the amount of air taken in by the diver per minute is not constant but changes, for example with the physical stress. In states of fear and panic, the air consumption can increase suddenly as a result of so-called hyperventilation. Furthermore, the amount of air removed is, of course, dependent on the respective ambient pressure and thus depends on how deep the diver is diving.
Therefore, the diver requires a monitoring device to be able to estimate the actual air consumption and the remaining possible bottom time under water.
Currently, in order to monitor the air supply divers use manometers which are connected to the breathing apparatus via a hose and indicate the current pressure of the air supply in the container. Since the pressu
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Mock Markus
Voellm Ernst B.
Asher Kimberly L.
UWATEC AG
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